Concerning the mass, we focus on the gas-giant and low-mass-brown-dwarf regime with \(M_{\mathrm {p}}\approx 1\) –\(20~M_{\mathrm {J}}\) . At much higher masses, the velocity of the gas at the shock is too high for H \(\alpha \)  to be generated in the postshock region, and the hydrogen lines are thought to be emitted by the accreting gas [1]}, [2]}.
